U.S. patent number 7,027,137 [Application Number 10/812,012] was granted by the patent office on 2006-04-11 for optical characteristics measuring apparatus, method and recording medium.
This patent grant is currently assigned to Advantest Corporation. Invention is credited to Eiji Kimura.
United States Patent |
7,027,137 |
Kimura |
April 11, 2006 |
Optical characteristics measuring apparatus, method and recording
medium
Abstract
An apparatus including a variable wavelength light source for
generating a variable wavelength light, a first light modulator for
inputting into a first optical fiber transmission line a first
incident light obtained by modulating the variable wavelength light
by a frequency of an electrical signal inputted, a first converter
for converting the first incident light, a fixed wavelength light
source for generating a fixed wavelength light, a signal source for
generating a reference electrical signal, a second light modulator
for inputting in a second optical fiber transmission line a second
incident light obtained by modulating the fixed wavelength light by
a frequency of the reference electrical signal and a second
converter for converting the second incident light and for
outputting the electrical signal into the first light
modulator.
Inventors: |
Kimura; Eiji (Saitama,
JP) |
Assignee: |
Advantest Corporation (Tokyo,
JP)
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Family
ID: |
18680935 |
Appl.
No.: |
10/812,012 |
Filed: |
March 30, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040179188 A1 |
Sep 16, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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09877202 |
Jun 11, 2001 |
6864967 |
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Foreign Application Priority Data
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Jun 15, 2000 [JP] |
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P2000-179716 |
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Current U.S.
Class: |
356/73.1 |
Current CPC
Class: |
G01M
11/333 (20130101); G01M 11/335 (20130101); G01M
11/338 (20130101); G01N 21/412 (20130101) |
Current International
Class: |
G01N
21/00 (20060101) |
Field of
Search: |
;356/73.1,364-367
;250/225,227.17 ;385/11,15,24,27,39,122 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 348235 |
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Dec 1989 |
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EP |
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2353591 |
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Feb 2001 |
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GB |
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WO99/43054 |
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Aug 1999 |
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WO |
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Primary Examiner: Nguyen; Tu T.
Attorney, Agent or Firm: Lowe Hauptman & Berner, LLP
Parent Case Text
RELATED APPLICATION
This application is a divisional of U.S. patent application Ser.
No. 09/877,202, filed Jun. 11, 2001 now U.S. Pat. No. 6,864,967.
Claims
What is claimed is:
1. An optical characteristic measuring apparatus for measuring
characteristics of devices under test having a first optical
transmission line letting light through only in a first direction
and a second optical transmission line letting light through only
in a second direction opposite to said first direction, said
apparatus comprising: a fixed wavelength light source for
generating a fixed wavelength light; a first light modulating
element for introducing into said first optical transmission line a
first incident light obtained by modulating said fixed wavelength
light with a first electrical signal, wherein said first incident
light exits from said first optical transmission line as a first
outgoing light; a first optical/electrical converting element for
converting the first outgoing light into a second electrical
signal; a variable wavelength light source for generating a
variable wavelength light; a signal source for generating a
reference electrical signal; a second light modulating element for
introducing into said second optical transmission line a second
incident light obtained by modulating said variable wavelength
light with said reference electrical signal, wherein said second
incident light exits from said second optical transmission line as
a second outgoing light; a second optical/electrical converting
element for converting the second outgoing light into the first
electrical signal and for outputting the first electrical signal
into said first light modulating element; and a third
optical/electrical converting element for converting a reflected
light, which is generated when said second light modulating element
introduces said second incident light into said second optical
transmission line, into a third electrical signal.
2. The optical characteristic measuring apparatus according to
claim 1, further comprising: a phase comparing element for
measuring a phase difference between a phase of the second
electrical signal output by said first optical/electrical
converting element and a phase of said reference electrical signal;
and a characteristic computing element for computing a group delay
characteristic or a dispersion characteristic of the devices under
test by using said phase difference.
3. The optical characteristic measuring apparatus according to
claim 1, further comprising: a phase comparing element for
measuring a phase difference between a phase of the third
electrical signal output by said third optical/electrical
converting element and a phase of said reference electrical signal;
and a characteristic computing element for computing a group delay
characteristic or a dispersion characteristic of the devices under
test by using said phase difference.
4. An optical characteristic measuring apparatus for measuring
characteristics of devices under test having a first optical
transmission line letting light through only in a first direction
and a second optical transmission line letting light through only
in a second direction opposite to said first direction, said
apparatus comprising: an optical/electrical converting element for
converting an outgoing light, which has penetrated and exits from
said first optical transmission line, into an electrical signal; a
variable wavelength light source for generating a variable
wavelength light; a signal source for generating a reference
electrical signal; a light modulating element for introducing into
said second optical transmission line an incident light obtained by
modulating said variable wavelength light with said reference
electrical signal; and a further optical/electrical converting
element for converting a reflected light, which is generated when
said light modulating element introduces said incident light into
said second optical transmission line, into a further electrical
signal.
5. The optical characteristic measuring apparatus according to
claim 4, further comprising: a phase comparing element for
measuring a phase difference between a phase of the electrical
signal output by said optical/electrical converting element and a
phase of said reference electrical signal; and characteristic
computing element for computing a group delay characteristic or a
dispersion characteristic of the devices under test by using said
phase difference.
6. The optical characteristic measuring apparatus according to
claim 4, further comprising: phase comparing element for measuring
a phase difference between a phase of the further electrical signal
output by said further optical/electrical converting element and a
phase of said reference electrical signal; and characteristic
computing element for computing a group delay characteristic or a
dispersion characteristic of the devices under test by using said
phase difference.
7. An optical characteristic measuring method of measuring
characteristics of devices under test having a first optical
transmission line letting light through only in a first direction
and a second optical transmission line letting light through only
in a second direction opposite to said first direction, said method
comprising: generating a fixed wavelength light; introducing into
said first optical transmission line a first incident light
obtained by modulating said fixed wavelength light with a first
electrical signal, wherein said first incident light exits from
said first optical transmission line as a first outgoing light;
converting the first outgoing light into a second electrical
signal; generating a variable wavelength light; generating a
reference electrical signal; introducing into said second optical
transmission line a second incident light obtained by modulating
said variable wavelength light with said reference electrical
signal, wherein said second incident light exits from said second
optical transmission line as a second outgoing light; converting
the second outgoing light and using the converted second outgoing
light as the first electrical signal in the step of modulating said
fixed wavelength light to obtain the first incident light; and
converting a reflected light, which is generated in the step of
introducing said second incident light into said second optical
transmission line, into a third electrical signal.
8. The method according to claim 7, further comprising: measuring a
phase difference between a phase of the second electrical signal
and a phase of said reference electrical signal; and computing a
group delay characteristic or a dispersion characteristic of the
devices under test by using said phase difference.
9. The method according to claim 7, further comprising: measuring a
phase difference between a phase of the third electrical signal and
a phase of said reference electrical signal; and computing a group
delay characteristic or a dispersion characteristic of the devices
under test by using said phase difference.
10. An optical characteristic measuring method of measuring
characteristics of devices under test having a first optical
transmission line letting light through only in a first direction
and a second optical transmission line letting light through only
in a second direction opposite to said first direction, said method
comprising: converting a first outgoing light, which has penetrated
and exits from said first optical transmission line, into an
electrical signal; generating a variable wavelength light;
generating a reference electrical signal; introducing into said
second optical transmission line an incident light obtained by
modulating said variable wavelength light with said reference
electrical signal; and converting a reflected light, which is
generated in the step of introducing said incident light into said
second optical transmission line, into a further electrical
signal.
11. The method according to claim 10, further comprising: measuring
a phase difference between a phase of the electrical signal and a
phase of said reference electrical signal; and computing a group
delay characteristic or a dispersion characteristic of the devices
under test by using said phase difference.
12. The method according to claim 10, further comprising: measuring
a phase difference between a phase of the further electrical signal
and a phase of said reference electrical signal; and computing a
group delay characteristic or a dispersion characteristic of the
devices under test by using said phase difference.
13. A computer-readable medium having a program of instructions for
execution by a computer to perform an optical characteristic
measuring process of measuring characteristics of devices under
test having a first optical transmission line letting light through
only in a first direction and a second optical transmission line
letting light through only in a second direction opposite to said
first direction, said optical characteristic measuring process
comprising: a fixed wavelength light generating processing for
generating a fixed wavelength light; a first light modulating
processing for introducing into said first optical transmission
line a first incident light obtained by modulating said fixed
wavelength light with a first electrical signal, wherein the first
incident light exits from said first optical transmission line as a
first outgoing light; a first optical/electrical converting
processing for converting the first outgoing light into a second
electrical signal; a variable wavelength light generating
processing for generating a variable wavelength light; a signal
generating processing for generating a reference electrical signal;
a second light modulating processing for introducing into said
second optical transmission line a second incident light obtained
by modulating said variable wavelength light with said reference
electrical signal, wherein the second incident light exits from
said second optical transmission line as a second outgoing light; a
second optical/electrical converting processing for converting the
second outgoing light and using the converted second outgoing light
as the first electrical signal in said first light modulating
processing; and a third optical/electrical converting processing
for converting a reflected light, which is generated when said
second incident light is introduced into said second optical
transmission line, into a third electrical signal.
14. The computer-readable medium according to claim 13, wherein
said optical characteristic measuring process further comprises: a
phase comparing processing for measuring a phase difference between
a phase of the second electrical signal and a phase of said
reference electrical signal; and a characteristic computing
processing for computing a group delay characteristic or a
dispersion characteristic of the devices under test by using said
phase difference.
15. The computer-readable medium according to claim 13, wherein
said optical characteristic measuring process further comprises: a
phase comparing processing for measuring a phase difference between
a phase of the third electrical signal and a phase of said
reference electrical signal; and a characteristic computing
processing for computing a group delay characteristic or a
dispersion characteristic of the devices under test by using said
phase difference.
16. A computer-readable medium having a program of instructions for
execution by a computer to perform an optical characteristic
measuring process of measuring characteristics of devices under
test having a first optical transmission line letting light through
only in a first direction and a second optical transmission line
letting light through only in a second direction opposite to said
first direction, said optical characteristic measuring process
comprising: an optical/electrical converting processing for
converting a first outgoing light, which has penetrated and exits
from said first optical transmission line, into an electrical
signal; a variable wavelength light generating processing for
generating a variable wavelength light; a signal generating
processing for generating a reference electrical signal; a light
modulating processing for introducing into said second optical
transmission line an incident light obtained by modulating said
variable wavelength light with said reference electrical signal;
and a further optical/electrical converting processing for
converting a reflected light, which is generated when said incident
light is introduced into said second optical transmission line,
into a further electrical signal.
17. The computer-readable medium according to claim 16, wherein
said optical characteristic measuring process further comprises: a
phase comparing processing for measuring a phase difference between
a phase of the electrical signal and a phase of said reference
electrical signal; and a characteristic computing processing for
computing a group delay characteristic or a dispersion
characteristic of the devices under test by using said phase
difference.
18. The computer-readable medium according to claim 16, wherein
said optical characteristic measuring process further comprises: a
phase comparing processing for measuring a phase difference between
a phase of the further electrical signal and a phase of said
reference electrical signal; and a characteristic computing
processing for computing a group delay characteristic or a
dispersion characteristic of the devices under test by using said
phase difference.
19. An optical characteristic measuring apparatus for measuring
characteristics of devices under test having a first optical
transmission line letting light through only in a first direction
and a second optical transmission line letting light through only
in a second direction opposite to said first direction, said
apparatus comprising: a fixed wavelength light source for
generating a fixed wavelength light; first light modulating means
for introducing into said first optical transmission line a first
incident light obtained by modulating said fixed wavelength light
with a frequency of a first electrical signal, wherein said first
incident light exits from said first optical transmission line as a
first outgoing light; first optical/electrical converting means for
converting, by a first optical/electrical conversion process, the
first outgoing light into a second electrical signal; a variable
wavelength light source for generating a variable wavelength light;
a signal source for generating a reference electrical signal;
second light modulating means for introducing into said second
optical transmission line a second incident light obtained by
modulating said variable wavelength light with said reference
electrical signal, wherein said second incident light exits from
said second optical transmission line as a second outgoing light;
second optical/electrical converting means for converting, by a
second optical/electrical conversion process, the second outgoing
light into the first electrical signal and for outputting the first
electrical signal into said first light modulating means; and third
optical/electrical converting means for converting, by a third
optical/electrical conversion process, a reflected light, which is
generated when said second light modulating means introduces said
second incident light into said second optical transmission line,
into a third electrical signal.
20. The optical characteristic measuring apparatus according to
claim 19, further comprising: phase comparing means for measuring a
phase difference between a phase of the second electrical signal
output by said first optical/electrical converting means and a
phase of said reference electrical signal; and characteristic
computing means for computing a group delay characteristic or a
dispersion characteristic of the devices under test by using said
phase difference.
21. The optical characteristic measuring apparatus according to
claim 19, further comprising: phase comparing means for measuring a
phase difference between a phase of the third electrical signal
output by said third optical/electrical converting means and a
phase of said reference electrical signal; and characteristic
computing means for computing a group delay characteristic or a
dispersion characteristic of the devices under test by using said
phase difference.
22. An optical characteristic measuring apparatus for measuring
characteristics of devices under test having a first optical
transmission line letting light through only in a first direction
and a second optical transmission line letting light through only
in a second direction opposite to said first direction, said
apparatus comprising: optical/electrical converting means for
converting, by an optical/electrical conversion process, an
outgoing light, which has penetrated and exits from said first
optical transmission line, into an electrical signal; a variable
wavelength light source for generating a variable wavelength light;
a signal source for generating a reference electrical signal; light
modulating means for introducing into said second optical
transmission line an incident light obtained by modulating said
variable wavelength light with said reference electrical signal;
and further optical/electrical converting means for converting, by
a further optical/electrical conversion process, a reflected light,
which is generated when said light modulating means introduces said
incident light into said second optical transmission line, into a
further electrical signal.
23. The optical characteristic measuring apparatus according to
claim 22, further comprising: phase comparing means for measuring a
phase difference between a phase of the electrical signal output by
said optical/electrical converting means and a phase of said
reference electrical signal; and characteristic computing means for
computing a group delay characteristic or a dispersion
characteristic of the devices under test by using said phase
difference.
24. The optical characteristic measuring apparatus according to
claim 22, further comprising: phase comparing means for measuring a
phase difference between a phase of the further electrical signal
output by said further optical/electrical converting means and a
phase of said reference electrical signal; and characteristic
computing means for computing a group delay characteristic or a
dispersion characteristic of the devices under test by using said
phase difference.
Description
BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to the measurement of the wavelength
dispersion characteristic of devices under test (DUT) such as fiber
pair, and in particular to the measurement of the wavelength
dispersion characteristic by connecting separate measuring methodes
on both ends of the DUT.
2. Description of the Related Art
In case of light being transmitted over a long distance, the
transmission of light only through an optical fiber will involve
considerable losses. Therefore, optical fiber transmission lines
combined with optical amplifiers (EDFA) for amplifying optical
signals are used for the optical fiber to prevent any possible
losses. The optical amplifiers let light through only in one
direction. Therefore, a bi-directional communication requires a
cable integrating an optical fiber transmission line transmitting
light in one direction and another optical fiber transmission line
transmitting light in the direction opposite to the one direction.
This cable is called a fiber pair.
The configuration of a fiber pair is shown in FIG. 6(a). An optical
fiber 112 combined with an optical amplifier 114 constitute an
optical fiber transmission line 110. The optical fiber transmission
line 110 lets light through to the right. An optical fiber 122
combined with an optical amplifier 124 constitutes an optical fiber
transmission line 120. The optical fiber transmission line 120 lets
light through to the left. An optical fiber transmission line 110
and a optical fiber transmission line 120 constitutes an optical
fiber pair 100a. Incidentally, two sets of fiber pairs are called
two fiber pairs as shown in FIG. 6(b). Fiber pairs 100a and 100b
constitute two fiber pairs 100.
The configuration of the measurement system for measuring the
wavelength characteristic of two fiber pairs is shown in FIG. 7. At
one end of a fiber pair 100a, which is one of two fiber pairs 100,
a variable wavelength light source 202 is connected and at another
end an O/E (optical/electric) converter 302 is connected. At one
end of a fiber pair 100b, which is one of the two fiber pairs 100,
a fixed wavelength light source 204 is connected, and at another
end an O/E (optical/electric) converter 304 is connected.
Incidentally, between the variable wavelength light sources 202,
204 and single fiber pairs 100a, 10b, a light modulator may be
installed.
To measure wavelength dispersion characteristics, the wavelength
.lamda.x of the variable wavelength light source 202 is swept,
while the wavelength .lamda.0 of the fixed wavelength light source
204 is fixed. The phase difference between the output signals of
the O/E converter 302 and the output signals of the O/E converter
304 is measured by the phase comparator 306, to measure the
wavelength dispersion characteristic of the two fiber pairs.
Here, in a bulk transmission line constituting a trunk line, two
fiber pairs may be secured. In most lines already laid out, often
only one fiber pair can be secured. Therefore, it is necessary to
measure the wavelength dispersion characteristic of a single fiber
pair.
SUMMARY OF INVENTION
Such a measuring method of the wavelength dispersion
characteristic, however, cannot be applied to a single fiber pair.
The reason is that two lines consisting of a line for letting a
fixed wavelength light through and another line for letting a
variable wavelength light through cannot be secured by a single
fiber pair.
Further, even if such a measuring method of wavelength dispersion
characteristic is applied to two fiber pairs 100, the measurements
may involve errors. In other words, due to physical quantitative
variations including variations in the temperature, stress, etc. of
the transmission line, the phase difference of light penetrating a
fiber pair 100a and another fiber pair 100b may vary due to factors
independent of wavelength. In such a case, the measurements may
involve errors. Therefore, it is desirable that wavelength
dispersion characteristics may be measured only by a single fiber
pair without using two fiber pairs.
Therefore, the present invention has an object of providing an
apparatus capable of measuring wavelength dispersion characteristic
and other characteristics only through a single fiber pair.
According to a first embodiment, an optical characteristic
measuring apparatus for measuring the characteristics of devices
under test having the first optical transmission line letting light
through in one direction only and the second optical transmission
line letting light through only on the direction opposite to the
aforementioned direction includes: a variable wavelength light
source for generating a variable wavelength light, the wavelength
of which is variable; a first light modulating unit for introducing
into the first optical transmission line the first incident light
obtained by modulating the variable wavelength light by the
frequency of the electrical signal inputted; a first
optical/electrical converting unit for converting by the
optical/electrical conversion process the first incident light
having penetrated the first optical transmission line; a fixed
wavelength light source for generating a fixed wavelength light,
the wavelength of which is fixed; a signal source for generating
reference electrical signals of given frequencies; a second light
modulating unit for injecting into the second optical transmission
line the second incident light obtained by modulating the fixed
wavelength light by the frequency of the reference electrical
signals; and a second optical/electrical converting unit for
converting by the optical/electrical conversion process the second
outgoing light having penetrated the second optical transmission
line; and for outputting the converted second outgoing light onto
the first light modulating unit.
According to an optical characteristic measuring apparatus thus
configured, once the wavelength of the fixed wavelength light is
set in such a way that wavelength dispersion may be small in the
second optical transmission line, the result of optical/electrical
conversion of the second outgoing light produces a small phase
difference than that of the second incident light. Thus, it is
possible to consider that the result of optical/electrical
conversion of the second outgoing light and the reference
electrical signals may have the identical frequencies and phases.
Thus, it is possible to consider that the first incident light may
be same as the result of modulation of the variable wavelength
light by the reference electrical signals. Thus, once the result of
optical/electrical conversion of the first outgoing light and the
reference electrical signals are obtained, the comparison of their
phases can lead to the discovery of phase differences related to
the first optical transmission line. And from the phase difference,
wavelength dispersion characteristic and other factors can be
computed.
According to a second embodiment, an optical characteristic
measuring apparatus for measuring the characteristics of devices
under test having the first optical transmission line for letting
light through only in one direction and the second optical
transmission line for letting light through only in the direction
opposite to the one direction includes: a fixed wavelength light
source for generating a fixed wavelength light, the wavelength of
which is fixed; a first light modulating unit for introducing into
the first optical transmission line the first incident light
obtained by modulating the fixed wavelength light by the frequency
of the electrical signals inputted; a first optical/electrical
converting unit for converting by the optical/electrical conversion
process the first outgoing light having penetrated the first
optical transmission line; a variable wavelength light source for
generating a variable wavelength light, the wavelength of which is
variable; a signal source for generating reference electrical
signals of given frequencies; a second light modulating unit for
introducing onto the second optical transmission line the second
incident light obtained by modulating the variable wavelength light
by the frequency of the reference electrical signals; and a second
optical/electrical converting unit for converting by the
optical/electrical conversion process the second outgoing light
having penetrated the second optical transmission line and for
outputting the converted second outgoing light onto the first light
modulating unit.
According to an optical characteristic measuring apparatus thus
configured, the result of optical/electrical conversion of the
second outgoing light will be electrical signals containing phase
differences related to the second optical transmission line.
Therefore, once the wavelength of the fixed wavelength light is set
in such a way that wavelength dispersion may be small in the first
optical transmission line, the first outgoing light containing
phase differences related to the second optical transmission line
and yet free of errors related to the first optical transmission
line can be obtained. Thus, once the result of optical/electrical
conversion of the first outgoing light and the reference electrical
signals are obtained, the comparison of their phases can lead to
the discovery of phase difference related to the second optical
transmission line. And from the phase difference, wavelength
dispersion characteristic and other factors can be computed.
According to a third embodiment, an optical characteristic
measuring apparatus for measuring the characteristics of devices
under test having the first optical transmission line letting light
through only in one direction and the second optical transmission
line letting light through only in the direction opposite to the
one direction includes: a first variable wavelength light source
for generating the first variable wavelength light, the wavelength
of which is variable; a first light modulating unit for introducing
onto the first optical transmission line the first incident light
obtained by modulating the first variable wavelength light by the
frequency of electrical signals inputted; a first
optical/electrical converting unit for converting by the
optical/electrical conversion process the first outgoing light
having penetrated the first optical transmission line; a second
variable wavelength light source for generating the second variable
wavelength light, the wavelength of which is variable; a signal
source for generating reference electrical signals of given
frequencies; a second light modulating unit for introducing into
the second optical transmission line the second incident light
obtained by modulating the second variable wavelength light by the
frequency of the reference electrical signals; and a second
optical/electrical converting unit for converting by the
optical/electrical conversion process the second outgoing light
having penetrated the second optical transmission line and for
outputting the converted second outgoing light onto the first light
modulating unit.
According to an optical characteristic measuring apparatus thus
configured, by using a first variable wavelength light source and a
second variable wavelength light source, the wavelength dispersion
characteristic and other factors of the first optical transmission
line and the second optical transmission line can be computed.
According to a fourth embodiment, the optical characteristic
measuring apparatus according to the second embodiment further
includes a third optical/electrical converting unit for converting
by the optical/electrical conversion process the reflected light
generated when the second light modulating unit introduces the
second incident light into the second optical transmission
line.
According to a fifth embodinment, the optical characteristic
measuring apparatus according to the first embodiment further
includes: a phase comparing unit for measuring the phase difference
between the electrical signals for measurement outputted by the
first optical/electrical converting unit and the reference
electrical signals; and a characteristic computing unit for
computing the group delay characteristic or the dispersion
characteristic of the devices under test by using the phase
difference.
According to a sixth embodiment, the optical characteristic
measuring apparatus according to the fourth embodiment further
includes: a phase comparing unit for measuring the phase difference
between the electrical signals for reflection measurement outputted
by the third optical/electrical converting unit and the reference
electrical signals; and a characteristic computing unit for
computing the group delay characteristic or the dispersion
characteristic of the devices under test.
According to a seventh embodiment, a light generating apparatus
used in an apparatus for measuring the characteristics of devices
under test having the first optical transmission line letting light
through only in one direction and the second optical transmission
line letting light through only on the direction opposite to the
one direction includes: a variable wavelength light source for
generating a variable wavelength light, the wavelength of which is
variable; a first light modulating unit for introducing into the
first optical transmission line the first incident light obtained
by modulating the variable wavelength light by the frequency of
electrical signals inputted; and a second optical/electrical
converting unit for converting by the optical/electrical conversion
process the second outgoing light having penetrated the second
optical transmission line and for outputting the converted second
outgoing light onto the first light modulating unit.
According to an eighth embodiment, an optical characteristic
measuring apparatus for measuring the characteristics of devices
under test having a first optical transmission line letting light
through only in one direction and a second optical transmission
line letting light through only in the direction opposite to the
one direction includes: a first optical/electrical converting unit
for converting by the optical/electrical conversion process the
first incident light having penetrated the first optical
transmission line; a fixed wavelength light source for generating a
fixed wavelength light, the wavelength of which is fixed; a signal
source for generating reference electrical signals of given
frequencies; and a second light modulating unit for introducing
into the second optical transmission line the second incident light
obtained by modulating the fixed wavelength light by the frequency
of the reference electrical signals.
According to an ninth embodiment, a light generating apparatus used
in a measuring apparatus of the characteristics of devices under
test having the first optical transmission line letting light
through only in one direction and the second optical transmission
line letting light through only in the direction opposite to the
one direction includes: a fixed wavelength light source for
generating a fixed wavelength light, the wavelength of which is
fixed; a first light modulating unit for introducing into the first
optical transmission line the first incident light obtained by
modulating the fixed wavelength light by the frequency of
electrical signals inputted; and a second optical/electrical
converting unit for converting by the optical/electrical conversion
process the second outgoing light having penetrated the second
optical transmission line and for outputting the converted second
outgoing light onto the first light modulating unit.
According to a tenth embodiment, an optical characteristic
measuring apparatus for measuring the characteristics of devices
under test having the first optical transmission line letting light
through only in one direction and the second optical transmission
line letting light through only in the direction opposite to the
one direction includes: a first optical/electrical converting unit
for converting by the optical/electrical conversion process the
first outgoing light having penetrated the first optical
transmission line; a variable wavelength light source for
generating a variable wavelength light, the wavelength of which is
variable; a signal source for generating reference electrical
signals of given frequencies; a second light modulating unit for
introducing into the second optical transmission line the second
incident light obtained by modulating the variable wavelength light
by the frequency of the reference electrical signals.
According to an eleventh embodiment, a light generating apparatus
used in a measuring apparatus of the characteristics of devices
under test having the first optical transmission line letting light
through only in one direction and the second optical transmission
line letting light through only in the direction opposite to the
one direction includes: a first variable wavelength light source
for generating the first variable wavelength light, the wavelength
of which is variable; a first light modulating unit for introducing
into the first optical transmission line the first incident light
obtained by modulating the first variable wavelength light by the
frequency of electrical signals inputted; and a second
optical/electrical converting unit for converting by the
optical/electrical conversion process the second outgoing light
having penetrated the second optical transmission line and for
outputting the converted second outgoing light onto the first light
modulating unit.
According to a twelfth embodiment, an optical characteristic
measuring apparatus for measuring the characteristics of devices
under test having the first optical transmission line letting light
through only in one direction and the second optical transmission
line letting light through only in the direction opposite to the
one direction includes: a first optical/electrical converting unit
for converting by the optical/electrical conversion process the
first outgoing light having penetrated the first optical
transmission line; a second variable wavelength light source for
generating the second variable wavelength light, the wavelength of
which is variable; a signal source for generating reference
electrical signals of given frequencies; a second light modulating
unit for introducing into the second optical transmission line the
second incident light obtained by modulating the second variable
wavelength light by the frequency of the reference electrical
signals.
According to a thirteenth embodiment, an optical characteristic
measuring method for measuring the characteristics of devices under
test having the first optical transmission line letting light
through in one direction only and the second optical transmission
line letting light through only on the direction opposite to the
aforementioned direction includes: a variable wavelength light
generating step for generating a variable wavelength light, the
wavelength of which is variable; a first light modulating step for
introducing into the first optical transmission line the first
incident light obtained by modulating the variable wavelength light
by the frequency of the electrical signal inputted; a first
optical/electrical converting step for converting by the
optical/electrical conversion process the first incident light
having penetrated the first optical transmission line; a fixed
wavelength light generating step for generating a fixed wavelength
light, the wavelength of which is fixed; a signal generating step
for generating reference electrical signals of given frequencies; a
second light modulating step for injecting into the second optical
transmission line the second incident light obtained by modulating
the fixed wavelength light by the frequency of the reference
electrical signals; and a second optical/electrical converting step
for converting by the optical/electrical conversion process the
second outgoing light having penetrated the second optical
transmission line; and for outputting the converted second outgoing
light onto the first light modulating step.
According to a fourteenth embodiment, an optical characteristic
measuring method for measuring the characteristics of devices under
test having the first optical transmission line for letting light
through only in one direction and the second optical transmission
line for letting light through only in the direction opposite to
the one direction includes: a fixed wavelength light generating
step for generating a fixed wavelength light, the wavelength of
which is fixed; a first light modulating step for introducing into
the first optical transmission line the first incident light
obtained by modulating the fixed wavelength light by the frequency
of the electrical signals inputted; a first optical/electrical
converting step for converting by the optical/electrical conversion
process the first outgoing light having penetrated the first
optical transmission line; a variable wavelength light generating
step for generating a variable wavelength light, the wavelength of
which is variable; a signal generating step for generating
reference electrical signals of given frequencies; a second light
modulating step for introducing onto the second optical
transmission line the second incident light obtained by modulating
the variable wavelength light by the frequency of the reference
electrical signals; and a second optical/electrical converting step
for converting by the optical/electrical conversion process the
second outgoing light having penetrated the second optical
transmission line and for outputting the converted second outgoing
light onto the first light modulating step.
According to a fifteenth embodiment, an optical characteristic
measuring method for measuring the characteristics of devices under
test having the first optical transmission line letting light
through only in one direction and the second optical transmission
line letting light through only in the direction opposite to the
one direction includes: a first variable wavelength light
generating step for generating the first variable wavelength light,
the wavelength of which is variable; a first light modulating step
for introducing onto the first optical transmission line the first
incident light obtained by modulating the first variable wavelength
light by the frequency of electrical signals inputted; a first
optical/electrical converting step for converting by the
optical/electrical conversion process the first outgoing light
having penetrated the first optical transmission line; a second
variable wavelength light generating step for generating the second
variable wavelength light, the wavelength of which is variable; a
signal generating step for generating reference electrical signals
of given frequencies; a second light modulating step for
introducing into the second optical transmission line the second
incident light obtained by modulating the second variable
wavelength light by the frequency of the reference electrical
signals; and a second optical/electrical converting step for
converting by the optical/electrical conversion process the second
outgoing light having penetrated the second optical transmission
line and for outputting the converted second outgoing light onto
the first light modulating step.
According to a sixteenth embodiment, a light generating method used
in a method for measuring the characteristics of devices under test
having the first optical transmission line letting light through
only in one direction and the second optical transmission line
letting light through only on the direction opposite to the one
direction includes: a variable wavelength light generating step for
generating a variable wavelength light, the wavelength of which is
variable; a first light modulating step for introducing into the
first optical transmission line the first incident light obtained
by modulating the variable wavelength light by the frequency of
electrical signals inputted; and a second optical/electrical
converting step for converting by the optical/electrical conversion
process the second outgoing light having penetrated the second
optical transmission line and for outputting the converted second
outgoing light onto the first light modulating step.
According to a seventeenth embodiment, an optical characteristic
measuring method for measuring the characteristics of devices under
test having a first optical transmission line letting light through
only in one direction and a second optical transmission line
letting light through only in the direction opposite to the one
direction includes: a first optical/electrical converting step for
converting by the optical/electrical conversion process the first
incident light having penetrated the first optical transmission
line; a fixed wavelength light generating step for generating a
fixed wavelength light, the wavelength of which is fixed; a signal
generating step for generating reference electrical signals of
given frequencies; and a second light modulating step for
introducing into the second optical transmission line the second
incident light obtained by modulating the fixed wavelength light by
the frequency of the reference electrical signals.
According to a eighteenth embodiment, a light generating method
used in a measuring method of the characteristics of devices under
test having the first optical transmission line letting light
through only in one direction and the second optical transmission
line letting light through only in the direction opposite to the
one direction includes: a fixed wavelength light generating step
for generating a fixed wavelength light, the wavelength of which is
fixed; a first light modulating step for introducing into the first
optical transmission line the first incident light obtained by
modulating the fixed wavelength light by the frequency of
electrical signals inputted; and a second optical/electrical
converting step for converting by the optical/electrical conversion
process the second outgoing light having penetrated the second
optical transmission line and for outputting the converted second
outgoing light onto the first light modulating step.
According to a nineteenth embodiment, an optical characteristic
measuring method for measuring the characteristics of devices under
test having the first optical transmission line letting light
through only in one direction and the second optical transmission
line letting light through only in the direction opposite to the
one direction includes: a first optical/electrical converting step
for converting by the optical/electrical conversion process the
first outgoing light having penetrated the first optical
transmission line; a variable wavelength light generating step for
generating a variable wavelength light, the wavelength of which is
variable; a signal generating step for generating reference
electrical signals of given frequencies; a second light modulating
step for introducing into the second optical transmission line the
second incident light obtained by modulating the variable
wavelength light by the frequency of the reference electrical
signals.
According to a twentieth embodiment, a light generating method used
in a measuring method of the characteristics of devices under test
having the first optical transmission line letting light through
only in one direction and the second optical transmission line
letting light through only in the direction opposite to the one
direction includes: a first variable wavelength light generating
step for generating the first variable wavelength light, the
wavelength of which is variable; a first light modulating step for
introducing into the first optical transmission line the first
incident light obtained by modulating the first variable wavelength
light by the frequency of electrical signals inputted; and a second
optical/electrical converting step for converting by the
optical/electrical conversion process the second outgoing light
having penetrated the second optical transmission line and for
outputting the converted second outgoing light onto the first light
modulating step.
A twenty-first embodiment includes an optical characteristic
measuring method for measuring the characteristics of devices under
test having the first optical transmission line letting light
through only in one direction and the second optical transmission
line letting light through only in the direction opposite to the
one direction including: a first optical/electrical converting step
for converting by the optical/electrical conversion process the
first outgoing light having penetrated the first optical
transmission line; a second variable wavelength light generating
step for generating the second variable wavelength light, the
wavelength of which is variable; a signal generating step for
generating reference electrical signals of given frequencies; a
second light modulating step for introducing into the second
optical transmission line the second incident light obtained by
modulating the second variable wavelength light by the frequency of
the reference electrical signals.
A twenty-second embodiment includes a computer-readable medium
having a program of instructions for execution by the computer to
perform an optical characteristic measuring process for measuring
the characteristics of devices under test having the first optical
transmission line letting light through in one direction only and
the second optical transmission line letting light through only on
the direction opposite to the aforementioned direction, the optical
characteristic measuring process including: a variable wavelength
light generating processing for generating a variable wavelength
light, the wavelength of which is variable; a first light
modulating processing for introducing into the first optical
transmission line the first incident light obtained by modulating
the variable wavelength light by the frequency of the electrical
signal inputted; a first optical/electrical converting processing
for converting by the optical/electrical conversion process the
first incident light having penetrated the first optical
transmission line; a fixed wavelength light generating processing
for generating a fixed wavelength light, the wavelength of which is
fixed; a signal generating processing for generating reference
electrical signals of given frequencies; a second light modulating
processing for injecting into the second optical transmission line
the second incident light obtained by modulating the fixed
wavelength light by the frequency of the reference electrical
signals; and a second optical/electrical converting processing for
converting by the optical/electrical conversion process the second
outgoing light having penetrated the second optical transmission
line; and for outputting the converted second outgoing light onto
the first light modulating processing.
A twenty-third embodiment includes a computer-readable medium
having a program of instructions for execution by the computer to
perform an optical characteristic measuring process for measuring
the characteristics of devices under test having the first optical
transmission line for letting light through only in one direction
and the second optical transmission line for letting light through
only in the direction opposite to the one direction, the optical
characteristic measuring process including: a fixed wavelength
light generating processing for generating a fixed wavelength
light, the wavelength of which is fixed; a first light modulating
processing for introducing into the first optical transmission line
the first incident light obtained by modulating the fixed
wavelength light by the frequency of the electrical signals
inputted; a first optical/electrical converting processing for
converting by the optical/electrical conversion process the first
outgoing light having penetrated the first optical transmission
line; a variable wavelength light generating processing for
generating a variable wavelength light, the wavelength of which is
variable; a signal generating processing for generating reference
electrical signals of given frequencies; a second light modulating
processing for introducing onto the second optical transmission
line the second incident light obtained by modulating the variable
wavelength light by the frequency of the reference electrical
signals; and a second optical/electrical converting processing for
converting by the optical/electrical conversion process the second
outgoing light having penetrated the second optical transmission
line and for outputting the converted second outgoing light onto
the first light modulating processing.
A twenty-fourth embodiment includes a computer-readable medium
having a program of instructions for execution by the computer to
perform an optical characteristic measuring process for measuring
the characteristics of devices under test having the first optical
transmission line letting light through only in one direction and
the second optical transmission line letting light through only in
the direction opposite to the one direction, the optical
characteristic measuring process including: a first variable
wavelength light generating processing for generating the first
variable wavelength light, the wavelength of which is variable; a
first light modulating processing for introducing onto the first
optical transmission line the first incident light obtained by
modulating the first variable wavelength light by the frequency of
electrical signals inputted; a first optical/electrical converting
processing for converting by the optical/electrical conversion
process the first outgoing light having penetrated the first
optical transmission line; a second variable wavelength light
generating processing for generating the second variable wavelength
light, the wavelength of which is variable; a signal generating
processing for generating reference electrical signals of given
frequencies; a second light modulating processing for introducing
into the second optical transmission line the second incident light
obtained by modulating the second variable wavelength light by the
frequency of the reference electrical signals; and a second
optical/electrical converting processing for converting by the
optical/electrical conversion process the second outgoing light
having penetrated the second optical transmission line and for
outputting the converted second outgoing light onto the first light
modulating processing.
A twenty-fifth embodiment includes a computer-readable medium
having a program of instructions for execution by the computer to
perform a light generating process used in a process for measuring
the characteristics of devices under test having the first optical
transmission line letting light through only in one direction and
the second optical transmission line letting light through only on
the direction opposite to the one direction, the light generating
process including: a variable wavelength light generating
processing for generating a variable wavelength light, the
wavelength of which is variable; a first light modulating
processing for introducing into the first optical transmission line
the first incident light obtained by modulating the variable
wavelength light by the frequency of electrical signals inputted;
and a second optical/electrical converting processing for
converting by the optical/electrical conversion process the second
outgoing light having penetrated the second optical transmission
line and for outputting the converted second outgoing light onto
the first light modulating processing.
A twenty-sixth embodiment includes a computer-readable medium
having a program of instructions for execution by the computer to
perform an optical characteristic measuring process for measuring
the characteristics of devices under test having a first optical
transmission line letting light through only in one direction and a
second optical transmission line letting light through only in the
direction opposite to the one direction, the optical characteristic
measuring process including: a first optical/electrical converting
processing for converting by the optical/electrical conversion
process the first incident light having penetrated the first
optical transmission line; a fixed wavelength light generating
processing for generating a fixed wavelength light, the wavelength
of which is fixed; a signal generating processing for generating
reference electrical signals of given frequencies; and a second
light modulating processing for introducing into the second optical
transmission line the second incident light obtained by modulating
the fixed wavelength light by the frequency of the reference
electrical signals.
A twenty-seventh embodiment includes a computer-readable medium
having a program of instructions for execution by the computer to
perform a light generating process used in a measuring process of
the characteristics of devices under test having the first optical
transmission line letting light through only in one direction and
the second optical transmission line letting light through only in
the direction opposite to the one direction, the light generating
process including: a fixed wavelength light generating processing
for generating a fixed wavelength light, the wavelength of which is
fixed; a first light modulating processing for introducing into the
first optical transmission line the first incident light obtained
by modulating the fixed wavelength light by the frequency of
electrical signals inputted; and a second optical/electrical
converting processing for converting by the optical/electrical
conversion process the second outgoing light having penetrated the
second optical transmission line and for outputting the converted
second outgoing light onto the first light modulating
processing.
A twenty-eight embodiment includes a computer-readable medium
having a program of instructions for execution by the computer to
perform an optical characteristic measuring process for measuring
the characteristics of devices under test having the first optical
transmission line letting light through only in one direction and
the second optical transmission line letting light through only in
the direction opposite to the one direction, the optical
characteristic measuring process including: a first
optical/electrical converting processing for converting by the
optical/electrical conversion process the first outgoing light
having penetrated the first optical transmission line; a variable
wavelength light generating processing for generating a variable
wavelength light, the wavelength of which is variable; a signal
generating processing for generating reference electrical signals
of given frequencies; a second light modulating processing for
introducing into the second optical transmission line the second
incident light obtained by modulating the variable wavelength light
by the frequency of the reference electrical signals.
A twenty-ninth embodiment includes a computer-readable medium
having a program of instructions for execution by the computer to
perform a light generating process used in a measuring process of
the characteristics of devices under test having the first optical
transmission line letting light through only in one direction and
the second optical transmission line letting light through only in
the direction opposite to the one direction, the light generating
process including: a first variable wavelength light generating
processing for generating the first variable wavelength light, the
wavelength of which is variable; a first light modulating
processing for introducing into the first optical transmission line
the first incident light obtained by modulating the first variable
wavelength light by the frequency of electrical signals inputted;
and a second optical/electrical converting processing for
converting by the optical/electrical conversion process the second
outgoing light having penetrated the second optical transmission
line and for outputting the converted second outgoing light onto
the first light modulating processing.
A thirtieth embodiment includes a computer-readable medium having a
program of instructions for execution by the computer to perform an
optical characteristic measuring process for measuring the
characteristics of devices under test having the first optical
transmission line letting light through only in one direction and
the second optical transmission line letting light through only in
the direction opposite to the one direction, the optical
characteristic measuring process including: a first
optical/electrical converting processing for converting by the
optical/electrical conversion process the first outgoing light
having penetrated the first optical transmission line; a second
variable wavelength light generating processing for generating the
second variable wavelength light, the wavelength of which is
variable; a signal generating processing for generating reference
electrical signals of given frequencies; a second light modulating
processing for introducing into the second optical transmission
line the second incident light obtained by modulating the second
variable wavelength light by the frequency of the reference
electrical signals.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing the configuration of an optical
characteristic measuring apparatus related to the first preferred
embodiment of the present invention.
FIG. 2 is a flowchart showing the operation of the first preferred
embodiment of the present invention.
FIG. 3 is a block diagram showing the configuration of an optical
characteristic measuring apparatus related to the second and third
preferred embodiments of the present invention.
FIG. 4 is a flowchart showing the operation of the second preferred
embodiment of the present invention.
FIG. 5 is a flowchart showing the operation of the third preferred
embodiment of the present invention.
FIGS. 6(a) and 6(b) are illustrations showing the structure of a
fiber pair according to the prior art.
FIG. 7 is an illustration showing the configuration of the
measuring system used to measure the wavelength dispersion
characteristic of two fiber pairs according to the prior art.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiments of the present invention are described
below with reference to the drawings.
The First Preferred Embodiment
FIG. 1 is a block diagram showing the configuration of an optical
characteristic measuring apparatus related to the first preferred
embodiment of the present invention. The optical characteristic
measuring apparatus related to the first preferred embodiment
includes a light source system 10 connected to an end of a fiber
pair 30 and a characteristic measuring system 20 connected to
another end of the fiber pair 30.
A fiber pair 30 includes a first optical fiber transmission line 32
and a second optical fiber transmission line 34. The optical fiber
transmission line 32 includes an optical fiber 32a and an optical
amplifier 32b that amplifies light and is connected to the midway
of the optical fiber 32a. The optical fiber transmission line 32
lets light through to the right. The optical fiber transmission
line 34 includes an optical fiber 34a and an optical amplifier 34b
that amplifies light and is connected to the midway of the optical
fiber 34a. The optical fiber transmission line 34 lets light
through to the left.
In the first preferred embodiment, the measurement of the first
optical fiber transmission line 32 is assumed, and the light source
system 10 is connected to the input (left) side of the first
optical fiber transmission line 32 and the characteristic measuring
system 20 is connected to the output (right) side.
The light source system 10 includes a variable wavelength light
source 12, a first light modulator 15, a second optical/electrical
converter 16 and an amplifier 18. The variable wavelength light
source 12 generates a variable wavelength light, the wavelength of
which is variable. The variable wavelength light source 12 can
sweep the wavelength .lamda.x of the variable wavelength light. The
first light modulator 15 modulates the variable wavelength light by
the frequency of electrical signals outputted by the second
optical/electrical converter 16. The first light modulator 15
normally contains lithium niobate (LN), but it can dispense with LN
provided that it can modulate. The light outputted by the first
light modulator (the first incident light) is inputted into the
first optical fiber transmission line 32. The second
optical/electrical converter 16 converts by the optical/electrical
conversion process the second outgoing light outputted from the
second optical fiber transmission line 34. The amplifier 18
amplifies the electrical signals outputted by the second
optical/electrical converter 16 and inputs them into the first
light modulator 15.
The first incident light inputted into the first optical fiber
transmission line 32 penetrates the first optical fiber
transmission line 32. The light having penetrated the first optical
fiber transmission line 32 is called as the first outgoing
light.
The characteristic measuring system 20 includes a fixed wavelength
light source 21, a first optical/electrical converter 22, a second
light modulator 23, an amplifier 24, a power source (signal source)
25, a phase comparator 26 and a characteristic computing section
28.
The fixed wavelength light source 21 generates a fixed wavelength
light, the wavelength of which is fixed. It is desirable to fix the
wavelength of the fixed wavelength light at a wavelength .lamda.0
at which the wavelength dispersion will be reduced to the minimum
in the second optical fiber transmission line 34.
The first optical/electrical converter 22 converts the first
outgoing light by the optical/electrical conversion process. The
power source (signal source) 25 generates electrical signals of a
frequency fin (reference electrical signals). The second light
modulator 23 modulates the fixed wavelength light by the frequency
fin of the electrical signals outputted by the power source
(signals source) 25. The second light modulator 23 includes lithium
niobate (LN). The light outputted by the second light modulator 23
(the second incident light) is inputted into the second optical
fiber transmission line 34. Incidentally, the second incident light
penetrates the second optical fiber transmission line 34. The light
having penetrated the second optical fiber transmission line 34 is
called as the second outgoing light. The amplifier 24 amplifies the
output of the first optical/electrical converter 22.
The phase comparator 26 receives the electrical signals generated
by the power source (signal source) 25 at a terminal Ref_In and the
electrical signals outputted by the amplifier 24 at a terminal
Prob_In. The phase comparator 26 takes the electrical signals
received at the terminal Ref_In as a reference for computing the
phase of the electrical signals received at the terminal
Prob_In.
The characteristic computing section 28 records the phases measured
by the phase comparator 26 and computes the group delay
characteristic and the wavelength dispersion characteristic of the
first optical fiber transmission line 32 based on the phases
recorded. The group delay characteristic can be computed from the
relationship between the phases measured by the phase comparator 26
and the modulation frequency fm. The wavelength dispersion
characteristic can be computed by differentiating the group delay
characteristic by the wavelength.
And now, the operation of the first preferred embodiment of the
present invention will be described with reference to the flowchart
in FIG. 2. On the left side the operation of the characteristic
measuring system 20 is shown, and on the right side the operation
of the light source system 10 is shown. Referring to the left side
to begin with, the fixed wavelength light source 21 generates a
fixed wavelength light (.lamda.=.lamda.0) (S20). Then, the fixed
wavelength light is modulated by the frequency fin of the reference
electrical signals generated by the power source (signal source)
(S22). And the process returns to the generation of the fixed
wavelength light source (S20).
The fixed wavelength light modulated by the frequency fin is the
second incident light. The second incident light penetrates the
second optical fiber transmission line 34 and is inputted into the
light source system 10 as the second outgoing light.
At this point, let us refer to the right side of FIG. 2. The
wavelength .lamda.x of the variable wavelength light is changed
(S10). Then, the variable wavelength light source 12 generates a
variable wavelength light (.lamda.=.lamda.x) (S12). The second
outgoing light is converted by the optical/electrical conversion
process by the second optical/electrical converter 16 (S14).
Here, the wavelength .lamda.0 of the fixed wavelength light is set
in such a way that the wavelength dispersion may be reduced to the
minimum in the second optical fiber transmission line 34.
Therefore, the result of the optical/electrical conversion of the
second outgoing light has a smaller phase difference than that of
the second incident light. Thus, the result of the
optical/electrical conversion of the second outgoing light and the
reference electrical signals can be considered to have the
identical frequencies and phases.
And the output of the second optical/electrical converter 16 is
amplified by the amplifier 18 (S16). Then, the variable wavelength
light is modulated by the first light modulator 15 by the frequency
of the electrical signals outputted by the second
optical/electrical converter 16 (S18). The frequency of the
electrical signals outputted by the second optical/electrical
converter 16 can be considered to be equal to the frequency fin of
the reference electrical signals. In the meanwhile, the light
modulated by the first light modulator 15 (the first incident
light) is inputted into the first optical fiber transmission line
32.
And now, the process returns to the change (sweep) of the
wavelength .lamda.x of the variable wavelength light (S10). And the
operation is terminated by switching off the power at any time
(S19).
Then, let us refer to the left of FIG. 2. The first incident light
penetrates the first optical fiber transmission line 32 and becomes
the first outgoing light. The first outgoing light is converted by
the optical/electrical conversion process by the first
optical/electrical converter 22 (S24). The electrical signals
outputted by the first optical/electrical converter 22 is amplified
by the amplifier 24 (S26). Then, the phase comparator 26 receives
the reference electrical signals generated by the power source
(signal source) 25 at its terminal Ref_In and the electrical
signals for measurement outputted by the amplifier 24 at its
terminal Prob_In. The phase comparator 26 takes the electrical
signals received at the terminal Ref_In as a reference for
computing the phase of the electrical signals received at the
terminal Prob_In (S28). And the phases measured are recorded at the
characteristic computing section 28.
And the phases of the electrical signals for measurement received
at the terminal Prob_In are affected by wavelength dispersion by
the first optical fiber transmission line 32. But, the phase of the
reference electrical signals received at the terminal Ref_In are
not affected by the wavelength dispersion by the first optical
fiber transmission line 32. Thus, the measurement of the phases of
the electrical signals for measurement received at the terminal
Prob_In by taking the reference electrical signals received at the
term Ref_In as references enables to compute the characteristics of
the first optical fiber transmission line 32.
When the light source system 10 stops operating, the characteristic
computing section 28 computes the group delay characteristic and
the wavelength dispersion characteristic of the first optical fiber
transmission line 32 (S29). The group delay characteristic can be
computed from the relationship between the phases measured by the
phase comparator 26 and the modulation frequency fm. The wavelength
dispersion characteristic can be computed by differentiating the
group delay characteristic by the wavelength.
According to the first preferred embodiment, it is possible to
measure the wavelength dispersion of the first optical fiber
transmission line 32 even if only one fiber pair can be
secured.
The Second Preferred Embodiment
The optical characteristic measuring apparatus related to the
second preferred embodiment is different from the first preferred
embodiment in that the characteristic measuring system 20 has a
variable wavelength light source and that the characteristic
measuring system 20 converts by the optical/electrical conversion
process and amplifies the reverberation of the second incident
light and compares the phases with those of the reference
electrical signals.
FIG. 3 is a block diagram showing the summarized configuration of
an optical characteristic measuring apparatus related to the second
preferred embodiment. Hereafter, the portions similar to the first
preferred embodiment will be marked by the codes of similarity and
their descriptions will be omitted.
The light source system 10 includes a fixed wavelength light source
11, a first light modulator 15, a second optical/electrical
converter 16 and an amplifier 18. The fixed wavelength light source
11 generates a fixed wavelength light, the wavelength of which is
fixed. It is preferable to set the wavelength of the fixed
wavelength light at a wavelength .lamda.0 at which the wavelength
dispersion will be reduced to the minimum in the first optical
fiber transmission line 32.
The characteristic measuring system 20 includes a variable
wavelength light source 29, a first optical/electrical converter
22a, a third optical/electrical converter 22b, a second light
modulator 23, amplifiers 24a and b, a power source (signal source)
25, a phase comparator 26 and a characteristic computing section
28.
The variable wavelength light source 29 generates a variable
wavelength light, the wavelength of which is variable. The variable
wavelength light source 21 can sweep the wavelength .lamda.y of the
variable wavelength light. The third optical/electrical converter
22b converts by the optical/electrical conversion process the
reverberations of the second incident light. The amplifier 24b
amplifies the electrical signals outputted by the third
optical/electrical converter 22b.
The phase comparator 26 receives the electrical signals generated
by the power source (signal source) 25 at a terminal Ref_In, the
electrical signals outputted by the amplifier 24a at a terminal
Prob_In 1 and the electrical signals for the measurement of
reverberations outputted by the amplifier 24b at a terminal Prob_In
2. The phase comparator 26 takes the electrical signals received at
the terminal Ref_In as a reference for computing the phase of the
electrical signals received at the terminal Prob_In 1 and the
terminal Prob_In 2.
The operation of the second preferred embodiment will be described
with reference to the flowchart in FIG. 4. On the left side the
operation of the characteristic measuring system 20 is shown, while
on the right side the operation of the light source system 10 is
shown. Let us refer to the left side to begin with. The wavelength
.lamda.y of the variable wavelength light is changed (S20). Then,
the variable wavelength light source 12 generates a variable
wavelength light (.lamda.=.lamda.y) (S21). Then, the variable
wavelength light is modulated by the frequency fin of the reference
electrical signals generated by the power source (signal source)
(S22). And then the process returns to the generation of the
variable wavelength light (S20).
The fixed wavelength light modulated by the frequency fin is the
second incident light. The second incident light penetrates the
second optical fiber transmission line 34 and is inputted into the
light source system 10 as the second outgoing light.
At this point, let us refer to the right side of FIG. 4. To begin
with, the fixed wavelength light source 21 generates a fixed
wavelength light (.lamda.=.lamda.0) (S10). The second outgoing
light is converted by the optical/electrical conversion process by
the second optical/electrical converter 16 (S14).
Here, the result of optical/electrical conversion of the second
outgoing light is affected by the wavelength dispersion of the
second optical fiber transmission line 34.
And the output of the second optical/electrical converter 16 will
be amplified (S16). Then, the variable wavelength light will be
modulated by the first optical/electrical converter 15 by the
frequency of the electrical signals outputted by the second
optical/electrical converter 16 (S18). In the meanwhile, the light
modulated by the first light modulator 15 (the first incident
light) will be injected into the first optical fiber transmission
line 32.
Here, the wavelength .lamda.0 of the fixed wavelength light is set
in such a way that the wavelength dispersion may be reduced to the
minimum in the first optical fiber transmission line 32. Thus, the
result of the optical/electrical conversion of the first outgoing
light is not affected by the wavelength dispersion of the first
optical fiber transmission line 32 and is affected only by the
wavelength dispersion of the second optical fiber transmission line
34.
And the process returns to the generation of the fixed wavelength
light (S10). In the meanwhile, the whole operation is terminated by
switching off the power at any time (S19).
Then, let us refer to the left of FIG. 4. The first incident light
penetrates the first optical fiber transmission line 32 and becomes
the first outgoing light. The first outgoing light is converted by
the optical/electrical conversion process by the first
optical/electrical converter 22a (S24). And the third
optical/electrical converter 22b converts by the optical/electrical
conversion process the reverberations of the second incident light
(S24). Then, the electrical signals outputted by the first
optical/electrical converter 22a and the third optical/electrical
converter 22b are respectively amplified by the amplifiers 24a and
b (S26). Then, the phase comparator 26 receives the reference
electrical signals generated by the power source (signal source) 25
at its terminal Ref_In, the electrical signals for measurement
outputted by the amplifier 24a at its terminal Prob_In 1 and the
electrical signals for measurement of reverberations outputted by
the amplifier 24b at its terminal Prob_In 2. The phase comparator
26 takes the electrical signals received at the terminal Ref_In as
a reference for computing the phase of the electrical signals
received at the terminals Prob_In 1 and Prob_In 2 (S28). And the
phases measured are recorded at the characteristic computing
section 28.
And the phases of the electrical signals received at the terminals
Prob_In 1 and Prob_In 2 are affected by wavelength dispersion by
the second optical fiber transmission line 34. But, the phase of
the reference electrical signals received at the terminal Ref_In is
not affected by wavelength dispersion by the second optical fiber
transmission line 34. Thus, the measurement of the phases of the
electrical signals received at the terminals Prob_In 1 and Prob_In
2 by taking the reference electrical signals received at the term
Ref_In as references enables to compute the characteristics of the
second optical fiber transmission line 34.
When the light source system 10 stops operating, the characteristic
computing section 28 computes the group delay characteristic and
the wavelength dispersion characteristic of the first optical fiber
transmission line 32 (S29). The group delay characteristic can be
computed from the relationship between the phases measured by the
phase comparator 26 and the modulation frequency fin. The
wavelength dispersion characteristic can be computed by
differentiating the group delay characteristic by the
wavelength.
According to the second preferred embodiment, it is possible to
measure the wavelength dispersion of the second optical fiber
transmission line 34 even if only one fiber pair can be
secured.
The Third Preferred Embodiment
The optical characteristic measuring apparatus related to the third
preferred embodiment is different from the second preferred
embodiment in that the light source system 10 has a variable
wavelength light source.
The configuration of the third preferred embodiment is described
with reference to FIG. 3. The light source system 10 includes a
variable wavelength light source 12, a first light modulator 15, a
second optical/electrical converter 16 and an amplifier 18. The
first variable wavelength light source 12 generates the first
variable wavelength light, the wavelength of which is variable. The
first variable wavelength light source 12 enables to sweep the
wavelength .lamda.x of the first variable wavelength light. The
configuration of other parts is similar to that of the second
preferred embodiment. Also the configuration of the characteristic
measuring system 20 is similar to that of the second preferred
embodiment. However, the variable wavelength light source 21 in the
second preferred embodiment is replaced by the second variable
wavelength light source 21 in the third preferred embodiment.
The operation of the third preferred embodiment will be described
with reference to the flowchart in FIG. 5. On the left side the
operation of the characteristic measuring system 20 is shown, while
on the right side the operation of the light source system 10 is
shown. Let us refer to the left side to begin with. The wavelength
.lamda.y of the second variable wavelength light is changed (S20).
Then, the variable wavelength light source 12 generates the second
variable wavelength light (.lamda.=.lamda.y) (S21). Then, the
second variable wavelength light is modulated by the frequency fm
of the reference electrical signals generated by the power source
(signal source) (S22). And then the process returns to the
generation of the second variable wavelength light (S20).
The fixed wavelength light modulated by the frequency fm is the
second incident light. The second incident light penetrates the
second optical fiber transmission line 34 and is inputted into the
light source system 10 as the second outgoing light.
At this point, let us refer to the right side of FIG. 5. The
wavelength .lamda.x of the first variable wavelength light is
changed (S10). Incidentally, the change (sweep) of .lamda.x and
that of .lamda.y will be synchronized. Then, the first variable
wavelength light source 12 generates the first variable wavelength
light (.lamda.=.lamda.x) (S12). The second outgoing light is
converted by the optical/electrical conversion process by the
second optical/electrical converter 16 (S14).
And the output of the second optical/electrical converter 16 will
be amplified (S16). Then, the first variable wavelength light will
be modulated by the first light modulator 15 by the frequency of
the electrical signals outputted by the second optical/electrical
converter 16 (S18). In the meanwhile, the light modulated by the
first light modulator 15 (the first incident light) will be
inputted into the first optical fiber transmission line 32.
And the process returns to the generation of the first variable
wavelength light (S10). In the meanwhile, the whole operation is
terminated by switching off the power at any time (S19).
Then, let us refer to the left of FIG. 5. The first incident light
penetrates the first optical fiber transmission line 32 and becomes
the first outgoing light. The first outgoing light is converted by
the optical/electrical conversion process by the first
optical/electrical converter 22a (S24). And the third
optical/electrical converter 22b converts by the optical/electrical
conversion process the reverberations of the second incident light
(S24). Then, the electrical signals outputted by the first
optical/electrical converter 22a and the third optical/electrical
converter 22b are amplified by the amplifiers 24a and b (S26).
Then, the phase comparator 26 receives the reference electrical
signals generated by the power source (signal source) 25 at its
terminal Ref_In, the electrical signals for measurement outputted
by the amplifier 24a at its terminal Prob_In 1 and the electrical
signals for measurement of reverberations outputted by the
amplifier 24b at its terminal Prob_In 2. The phase comparator 26
takes the electrical signals received at the terminal Ref_In as a
reference for computing the phase of the electrical signals
received at the terminals Prob_In 1 and Prob_In 2 (S28). And the
phases measured are recorded at the characteristic computing
section 28.
When the light source system 10 stops operating, the characteristic
computing section 28 computes the group delay characteristic and
the wavelength dispersion characteristic of the first optical fiber
transmission line 32 (S29). The group delay characteristic can be
computed from the relationship between the phases measured by the
phase comparator 26 and the modulation frequency fm. The wavelength
dispersion characteristic can be computed by differentiating the
group delay characteristic by the wavelength.
According to the third preferred embodiment, it is possible to
measure the wavelength dispersion of the first optical fiber
transmission line 32 and the second optical fiber transmission line
34 even if only one fiber pair can be secured.
In the meanwhile, the embodiment described above can be realized by
having a media reading apparatus of a computer provided with a CPU,
a hard disk, memory media (a floppy disk, a CD-ROM, etc.) read a
program executing various functions described above and installing
the program on a hard disk. In this way, the functions described
above can be performed.
According to the present invention, it is possible to measure group
delay characteristic and other characteristics even if the device
under test is a single fiber pair.
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